A wideband tuner is capable of detecting composite signals from multiple sources such as terrestrial base stations and satellites. A typical wideband tuner includes analog and digital subsections. Often, the analog subsection can respond to signals much wider than the signaling frequency bandwidth. Signals that are not in a signaling frequency band of interest but in the adjacent frequency bands can act as blocker signals that block signals of interest. These blocker signals can appear randomly or periodically with a varying duty cycles. The amplitude level of these signals relative to a desired signal of interest may vary significantly.
Wideband tuners may employ automatic gain control (AGC) circuitry in order to regulate the received signal strength. For example, if a received signal strength is weak the AGC circuit boosts the receiver gain to minimize the front-end noise and boost the signal level (attack mechanism). Conversely, if the received signal strength is strong, the AGC circuit attenuates front-end receiver gain stages to avoid signal clipping and operation of the receiver in a non-linear region. A wideband tuner operates based on a fast attack/slow decay mechanism for responding to changing signal conditions.
A fast attack/slow decay approach present in the a AGC circuit may not be fast enough to respond quickly to the appearance and disappearance of these blocker signals. Moreover, a strong incoming blocker signal can drive the tuner into its non-linear region of operation in which it cannot receive a signal of interest. Furthermore, a strong blocker can reduce the tuner gain into its noise limited region.